Abstracts:

First Seminar:  Dynamics of a rotating, strongly interacting Fermi gas

by: Stefan Riedl

We investigate the dynamics of a rotating, strongly interacting Fermi gas of 6Li atoms confined in a harmonic trap. To detect the angular momentum of the gas we exploit the fact that the behavior of a collective quadrupole excitation depends on the rotation frequency of the gas. We measure the lifetime of the angular momentum for different temperatures and trap anisotropies. The measurements show the expected exponential decay of the angular momentum and the decrease of the lifetime with increasing trap anisotropy. We find particularly long lifetimes of rotation because of the strong interactions, in agreement with recent theory. The ability to measure the angular momentum also allows us to determine the moment of inertia of the gas. This is of particular interest since superfluidity leads to quenching of the moment of inertia.

Second Seminar: Heteronuclear Feshbach resonances in a mixture of ultracold ⁸⁷ Rb and ¹³³ Cs

by: Karl Pilch

We present the first observation of heteronuclear Feshbach resonances in a bosonic mixture of ultracold ¹³³ Cs and ⁸⁷ Rb. One of the key ingredients of the all-optical approach of sample preparation is the use of simultaneous degenerate Raman sideband cooling on both species. We observe interspecies Feshbach resonances in three-body loss measurements by recording the remaining number of atoms after some fixed hold time in the optical dipole trap as a function of the value for the magnetic offset field. We find an unexpected rich structure of interspecies Feshbach resonances for two different incoming collisional channels within a magnetic field between 20G to 300G. We currently measure the binding energy of the molecular states related to some of the observed Feshbach resonances. A consistent assignment of the observed Feshbach resonances will allow us to quantify the interspecies collisional properties. We discuss potential pathways towards obtaining a double-degenerate bosonic quantum gas and towards the production of ground state RbCs molecules.